Sound travel at 1100ft/s, the smallest resonance frequency of sound wave in 6" tube closed at 1 end is

Question

A 275 Hz

B 550Hz

C1100 Hz

D 2200Hz

E 4400 Hz

the correct answer is B but i can't find how it can be 550Hz...

Answer 1

thus λ=4*6inch = 24inch, while λ=v/f; or 24in = (1100*12) / f, hence f=1100*12/24 =550Hz;

why λ=4*6inch? Because node will be observed at closed end, max amplitude – at open end; therefore the tube contains only ¼ of standing wave in it;